A settling device of this kind is known from EP-A1-0,244,029 and EP-A1-0,193,999. These publications describe caps which are fitted horizontally in overlapping connection and which are fitted to limit the top edge of a fermentation chamber so as to form a settling chamber above it. The caps trap gas bubbles rising from the fermentation chamber, whilst transfer of remaining fluid in the upward direction between the caps is permitted. The trapping of gas bubbles ensures that the fluid in the settling chamber is relatively still relative to the fluid in the fermentation chamber, the latter fluid being in a state of motion as a result of the rising gas bubbles. The fact that the fluid present in the settling chamber is relatively still means that particles which are present therein and have been carried along from the fermentation chamber are able to settle, these particles being able to fall back between the caps to the fermentation chamber. The settling devices known from these publications have the drawback, however, that, when major turbulences occur, bubbles can easily be passed between the caps and then make their way into the settling chamber, thereby having an adverse effect upon the settling in the settling chamber. Smaller gas bubbles, in particular will slip through easily between the caps.
The object of the present invention is, inter alia, to eliminate the above-mentioned drawbacks.